Purpose. Phosducin (Phd) selectively binds G-protein subunits (Gβy) of retina, brain and liver. Previously, we and others identified phosducin-like proteins (PhLPs) and wanted to determine their Gβy binding capability and discovered that several isoforms (phosducin-like orphan proteins: PhLOPs) lack Gβy binding. Methods. Human retina (hr) A.MAX library was screened with a phosducin epitope domain PCR product and identified the Phdl, plus 3 new homologues, renamed PhLP2, PhLOP3. and PhLOP4. Results. Distinct PhLP/PhLOP peptide antibodies were prepared and immunocytochemistry showed these retinal isoforms are present in all tissues examined. Whereas Phd is observed both in rod and cone photoreceptors, PhLP2 is selective for cone photoreceptors. Biochemical and functional interactions were verified with transducin Gβy in vitro and with surface plasmon resonance technology with GST/ constructs for Phdl and PhLP2; however, neither PhLOP3 nor PhLOP4 bound Gβy. Conclusion-4 These findings demonstrate that retinal phosducin and its isoforms are ubiquitously distributed in body tissues where cell-specific phosducins participate in the modulation of distinct G-protein signaling pathways. PhLOP isoforms, with either amino acid terminus truncation or alteration of the predicted structural domain (TGPKGVINDWR), may serve other critical functions in the signaling pathway.
|Original language||English (US)|
|Journal||Investigative Ophthalmology and Visual Science|
|State||Published - Dec 1 1997|
ASJC Scopus subject areas
- Sensory Systems
- Cellular and Molecular Neuroscience